Here is the OA for all the questions (OG 10th):

80.
This question asks you to identify the primary focus of the passage.
The best answer is B. The author describes the new theoretical model in the first paragraph; in the
final paragraph the author states that the data obtained from actual observations, which are
discussed in the second and third paragraphs, is consistent with the new theoretical model.
Choice A is not correct; the computer model confirmed the astronomers’ hypothesis that meteor
streams broaden with time, and although the model yielded an unexpected result, the passage does
not contrast the predictions yielded by competing theories. Choice C and D are not correct because
the passage makes no reference to further areas for research, and only a single phenomenon is
described in the passage. And choice E is not correct because it reverses the order of events. The
model yielded a prediction that was subsequently confirmed by observational data, the model was
not constructed to explain the data.
81.
This question asks you to identify an accurate statement about meteor streams. Choice C, the best
answer, restates information about the composition of meteor streams from the first sentence of
the passage.
Choice A is not correct. The passage discusses the influence of planetary gravitation on meteor
streams but says nothing about its influence on the orbits of comets. According to the passage, it is
planetary gravitation, not the gravitational fields of comets, that causes meteor streams to increase
in size, so choice B is not correct. And choice D and E are not correct answers because the passage
says nothing about the composition of comets or the role that meteor streams play in their further
disintegration.
82.
This question asks what the author says about the purpose of the research described in the first
paragraph.
The best answer is D. According to the author, the purpose of the computer-modeling experiment
was to test the hypothesis that meteor streams broaden with time.
Choice A is not correct; although the observational data described in the last paragraph allowed
scientists to estimate the age of the Geminid stream, this data was analyzed to confirm a surprising
prediction made by the computer model. This analysis was not part of the original experiment.
Choice B is also incorrect. Although the experiment yielded a surprising prediction about a
particular feature of meteor streams, the purpose of the experiment was to determine whether
meteor streams broaden with time, not to identify the various structural features of meteor streams.
Choice C is not correct because the experiment was undertaken to test a general hypothesis about
meteor streams. It was not undertaken to explore the nature of any particular meteor stream, and
328
the passage never suggests that the actual meteor streams used in the computer model was
“particularly interesting.”
Choice E is not correct. Although the computer model did confirm the astronomers’ hypothesis,
the purpose of the experiment was not to show that such models are useful.
83.
This question asks you to make an inference about what would most probably be observed during
the Earth’s passage through a meteor stream if the conventional theories mentioned in the passage
were correct. According to line 18-20, the conventional theories predicted that the meteor stream
would be most dense at the center. The computer model, one the other hand, predicted that a
meteor stream would come to resemble a thick-walled, hollow pipe (lines 21-22). The passage
states that, if the computer model were correct, two peak periods of meteor activity would be
observed as the Earth passed through the walls of the “pipe” (lines 28-31). According to lines
36-38, observational data confirmed the prediction of the computer model. If, on the other hand,
the conventional theories were correct, it can be inferred that a bifurcation of meteor activity
would not be observed; instead, it can be inferred that scientists would expect to observe a single
peak of meteor activity as the Earth passed through the dense center of the stream. Choice A
identifies this single peak of activity as the most likely observation if the conventional theories
were correct.
Choice B and D are not correct because they describe meteor activity that is either steady or
erratic, neither of which is consistent with the conventional theories. Choice C describes meteor
activity more in line with the bifurcation predicted by the computer model, rather than the single
peak of activity that the conventional theories would suggest. Choice E is incorrect because the
passage says that meteor showers occur whenever the Earth passes through a meteor stream; it
cannot be inferred that either theory would predict otherwise.
84.
This question asks for the reason given in the passage for a characteristic feature of meteor
streams. According to lines 1-7, the dust particles in a meteor stream eventually surround a
comet’s original orbit because of the different velocities at which they are ejected, as stated in
choice A, the best answer.
Choice B is directly contradicted by information in the passage (lines 8-10). The other answer
choices re incorrect because the passage does not say that the dust particles become part of the
meteor stream at different times, or that their velocity slows over time, or that their ejection
velocity is slower than that of the comet.
85.
This question asks you to identify a prediction that can be derived from both the conventional
theories about meteor streams and the new computer-derived model. You must base your answer
on information that is suggested by, but not expressly stated in, the passage.
According to lines 7-8 of the passage, the conventional theories hypothesized that meteor streams
should broaden with time, and the computer simulation confirmed this hypothesis. The passage
also suggests that the time it takes for the Earth to cross a meteor stream (and, by implication, the
duration of the resulting meteor shower) is directly related to the breadth of the stream (lines
23-28). From these pieces of information, which are supported by both the conventional theories
329
and the new computer-derived theory, it can be inferred that on average the meteor showers
caused by older (and therefore broader) meteor streams would be longer in duration than those
caused by very young (and therefore narrower) meteor streams, as stated in D, the best answer.
Choice A is incorrect because it contradicts the predictions of both the conventional theories (that
the particles will be most dense at the center of the stream) and the computer model (that the
stream will resemble a thick-walled, hollow pipe). Choice C is also incorrect because it is
inconsistent with the conventional theories that suggested the distribution of dust in a meteor
stream is denser at the center. And choices B and E are incorrect because the theories discussed in
the passage do not suggest anything about the likelihood that the Earth’s orbit will cross that of
any particular meteor stream, nor do they suggest anything about the size of the dust particles that
compose meteor streams.
86.
This question asks you to draw an inference from information in the last paragraph of the passage.
The best answer is C. According to the passage, the Geminid meteor shower occurs yearly;
because meteor showers occur whenever the Earth passes through a meteor stream, one can infer
that the Earth crosses the Geminid stream once every year.
Choice A is incorrect because the passage provides no information from which to generalize about
the age of meteor streams. Choice B, which is directly contradicted by lines 31-32, is also
incorrect. Choice D is incorrect. In lines 25-28, the passage says that the Earth would take just
over a day to cross the stream if the stream were 5,000 years old. However, in lines 38-42 the
passage states that in fact an average of only 19 houses elapsed between the time that the Earth
entered the stream until the time that it exited, leading researchers to conclude that the stream is
only about 3,000 years old. Choice E is incorrect because the passage says only that planetary
gravitational fields perturb the orbits of dust particles in a meteor stream; it does not say that the
effect of the Earth’s gravitation is greater than that of other planets.
87.
This question asks you to identify an assumption underlying the last sentence of the passage. In
this sentence, the author of the passage draws a conclusion about the age of the Geminid stream.
This conclusion is based on two pieces of information. The first is the length of time the Earth
would take to cross the computer-model Geminid stream if the stream were 5,000 years old (lines
24-28). The second is the actual elapsed time between the two peaks of meteor activity predicted
by the computer model (lines 36-40). In concluding from this information that the Geminid stream
is actually only 3,000 years old, the author is assuming the accuracy of the computer model, as
stated in E, the best answer.
Choice A is incorrect because the passage says that the time the Earth takes to cross the stream
would vary from year to year (lines 32-34) and that 19 hours was the average time, not the exact
time, observed from 1970 to 1979 (lines 36-40). Choices B and C are incorrect because the
passage does not suggest anything about the current state of the comet associated with the
Geminid stream or about the expected longevity of the stream. Choices D is incorrect because the
computer model is said to confirm the broadening predicted by the conventional theories; the fact
that the model projected the positions of the particles in the stream over a 5,000-year period does
not suggest that researchers expected the stream to be older (and therefore broader) than it turned
out to be.

“Moving at a little over 1,500,000 miles per day around its orbit, the Earth would take, on average, just over a day to cross the hollow, computer-model Geminid stream if the stream were 5,000 years old. Two brief periods of peak meteor activity during the shower would be observed, one as the Earth entered the thick-walled "pipe" and one as it exited. There is no reason why the Earth should always pass through the stream's exact center, so the time interval between the two bursts of activity would vary from one year to the next.”

I am having a hard time to understand this part, can someone please explain. It says it takes average one day for the earth to cross the stream, so isn't the observation of peak meteor activity would be within 24 hours? But later it says "the time interval between the two bursts of activity would vary from one year to the next", what does that mean? How can the time taken to enter and exit the stream all the sudden jump from one day to one year? What did I missed?

IMAGINE

a big hollow pipe

Now earth can pass through the centre,
Earth can also pass making a chord of a circle

Right??

When Earth passes through the centre, the average time will be x
when it passes somewhere other than the centre, the average time will be less than x

I hope you understood the twin peak shower, when earth passes through the circle


If I was quick and helpful, I'd love to see your gratitude in form of a like to this post.

Glad to help Meisme
_________________

Can someone explain Q7? I understand why other options are not correct but how can one infer C to be correct?
_________________

DiyaDutta
LOOK Carefully
(A) Most meteor streams it encounters are more than 2,000 years old.
TRICKSTER!!! Last sentence says 3000 yr old

(B) When passing through a meteor stream, it usually passes near to the stream’s center.
There is no reason why the Earth should always pass through the stream's exact center, so the time interval between the two bursts of activity would vary from one year to the next.

(C) It crosses the Geminid meteor stream once every year.
KEEP IT, couldn't find negation


(D) It usually takes over a day to cross the actual Geminid meteor stream.
a secondary burst of meteor activity being clearly visible at an average of 19 hours (1,200,000 miles) after the first burst

(E) It accounts for most of the gravitational perturbation affecting the Geminid meteor stream.
MOST OF THE???

I hope I was helpful, and if I was, your gratitude in the form of a like to my post is very valuable
_________________

Overall - fairly confused at first. I was having difficulties trying to figure out what was going on with latter pargraphs.
Passage Map:
P1: To describe meteor stream theories and proliferation of computer model
P2: to state technical info. regarding streams
P3: to discuss evidence on streams

Q6
Most of this is contained in P1.
Conventional theories predict that particles are more dense toward the centre of meteor streams whereas computer models predict that streams broaden over time.
However, the computer model came to show that gradually particles grouped to form a thick-walled, hollow pipe.

What is a prediction we can make from both theories?
A- this is clearly false since we know that particles clump in two regions (outer edges of the hollow-pipe)
B - we can't really support when and what meteor streams the Earth crosses based on the theories alone. Incorrect
C cannot be derived from the conventional theory. Incorrect
D is supportable. Here's why:
P1 states that the meteor streams "broaden over time" - allowing us to conclude that the hollow forms as the meteor stream ages. Earth passes through the hollow "thick pipe.
Thus it can be inferred that the older a meteor shower, the longer it would take to pass through the first peak of activity, then pass through the hollow, then pass through the second peak as the older meteor showers are broader than younger.
E is incorrect - we know nothing of the relative size of the dust particles.

Q7
The first sentence states "yearly geminid meteor shower"
Therefore C is correct - the Earth passes through the meteor stream once per year
A is incorrect because we don't have any comparative info to identify the age of other streams.
B is incorrect because we are told in p2 "there is no reason the earth should ALWAYS pass through the stream's exact center"
D is incorrect because we are only given an average of 19 hours "after the first burst" before Earth hits the second stream, so clearly the Earth could take a lot longer to pass through both streams completely.
E is incorrect because there is no such evidence commenting on the sun's involvement in earth's orbital course through the meteor streams discussed.
_________________

Can experts please explain why C over D?

7. It can be inferred from the last paragraph of the passage that which of the following must be true of the Earth as it orbits the Sun?

(A) Most meteor streams it encounters are more than 2,000 years old.
(B) When passing through a meteor stream, it usually passes near to the stream???s center.
(C) It crosses the Geminid meteor stream once every year.
(D) It usually takes over a day to cross the actual Geminid meteor stream.
(E) It accounts for most of the gravitational perturbation affecting the Geminid meteor stream.

At first, I didn't know why there is "the Sun" here as there is no info about the Sun in the passage.
Then I translated the part "must be true of the Earth as it orbits the Sun" into "must be true of the Earth in one year" as the Earth completes its orbit around the Sun in 1 year.

We know that "the time interval between the two bursts of activity would vary from one year to the next." -> meaning: the Geminid meteor shower is observed to occur every year. Thus in 1 year, the Earth passes thru the Geminid stream once.
_________________

Kindly provide explanations for all questions. Thank you.

1. The primary focus of the passage is on which of the following?

(A) Comparing two scientific theories and contrasting the predictions that each would make concerning a natural phenomenon

….incorrect, this passage doesn’t compare two scientific theories





(B) Describing a new theoretical model and noting that it explains the nature of observations made of a particular natural phenomenon

….correct

…..at first I just think option(B) only partially correct, this is only about the former half of para1

SEE para1
……In the model, the particles were randomly distributed throughout a computer simulation of the orbit of an actual meteor stream….


…..“Conventional theories”( not new theoretical model), however, predicted that the distribution of particles would be increasingly dense toward the center of a meteor stream.

However “I DIDN’T NOTICE THE LATER HALF OF OPTION(B)”, which accurately describes para2&3---meteor shower



(C) Evaluating the results of a particular scientific experiment and suggesting further areas for research

….incorrect, here we doesn’t evaluate anything





(D) Explaining how two different natural phenomena are related and demonstrating a way to measure them

….incorrect
This is an option which I thought is right at first


Whenever the Earth passes through a meteor stream, a meteor shower occurs.
----para2 is about natural phenomena


Para1 is about the introduction to meteor stream(a natural phenomena) and its movement led to the argument of new computer-model

Para2 insert “meteor shower” into para1’s view of “meteor stream”, though we can say para1&2 are both related, but the passage’s main focus doesn’t about how two phenomena related


The Geminid data between 1970 and 1979 shows just such a
bifurcation, a secondary burst of meteor activity being clearly
visible at an average of 19 hours (1,200,000 miles) after the first
burst. The time intervals between the bursts suggest the actual
Geminid stream is about 3,000 years old.
---- demonstrating a way to measure “them”, here the passage
only measure para2&3 rather than para1





(E) Analyzing recent data derived from observations of an actual phenomenon and constructing a model to explain the data

---only partially correct, here in the passage we analyze data both computer modeling as well as actual phenomenon





2. According to the passage, which of the following is an accurate statement concerning meteor streams?


A meteor stream is composed of dust particles that have been ejected from a parent comet at a variety of velocities. These particles follow the same orbit as the parent comet, but due to their differing velocities they slowly gain on or fall behind the disintegrating comet until a shroud of dust surrounds the entire cometary orbit. Astronomers have hypothesized that a meteor stream should broaden with time as the dust particles' individual orbits are perturbed by planetary gravitational fields.




(A) Meteor streams and comets start out with similar orbits, but only those of meteor streams are perturbed by planetary gravitation.

…incorrect
At first I choose this choice and cannot quite understand why its wrong
Its that, if you reason back from (C) could we understand the theorem behind
----if “Meteor streams are composed of dust particles derived from comets.”
----as the author mention in the passage that “meteor streams are perturbed by planetary gravitation.”
----generally speaking, comets will also perturbed by planetary gravitation.”



(B) Meteor streams grow as dust particles are attracted by the gravitational fields of comets.

para1
Astronomers have hypothesized that a meteor stream should broaden with time as the dust particles' “individual orbits” are perturbed by planetary gravitational fields.


notice the difference between sentence in para1 and the statement of (B), though they’re very similar, the sentence clearly indicates its dust particles’ “individual orbits” will influence the “planetary” gravitational field rather than “comet’s”




(C) Meteor streams are composed of dust particles derived from comets.
….correct

sentence in para1 clearly correspond to the statement of (C)
A meteor stream is composed of dust particles that have been ejected from a parent comet at a variety of velocities.



(D) Comets may be composed of several kinds of materials, while meteor streams consist only of large dust particles.

the article doesn’t hint anything about the composition of comet and meteor stream


(E) Once formed, meteor streams hasten the further disintegration of comets.

nowhere in the article mention the “hasten of the further disintegration of comets”



3. The author states that the research described in the first paragraph was undertaken in order to





(A) determine the age of an actual meteor stream

Its para2&3, not para1

(B) identify the various structural features of meteor streams
(C) explore the nature of a particularly interesting meteor stream
(D) test the hypothesis that meteor streams become broader as they age

….correct



(E) show that a computer model could help in explaining actual astronomical data





4. Q. It can be inferred from the passage that which of the following would most probably be observed during the Earth's passage through a meteor stream if the conventional theories mentioned in line 18 were correct?

Conventional theories, however, predicted that the distribution of particles would be increasingly dense toward the center of a meteor stream. Surprisingly, the computer-model meteor stream gradually came to resemble a thick-walled, hollow pipe.




(A) Meteor activity would gradually increase to a single, intense peak, and then gradually decline.

….correct
Below is the new computerized model’s view, opposite to conventional one

Two brief periods of peak meteor activity during the shower would be observed, one as the Earth entered the thick-walled "pipe" and one as it exited.



(B) Meteor activity would be steady throughout the period of the meteor shower.
(C) Meteor activity would rise to a peak at the beginning and at the end of the meteor shower.
(D) Random bursts of very high meteor activity would be interspersed with periods of very little activity.
(E) In years in which the Earth passed through only the outer areas of a meteor stream, meteor activity would be absent.





5. According to the passage, why do the dust particles in a meteor stream eventually surround a comet’s original orbit?



(A) They are ejected by the comet at differing velocities.
….correct
A meteor stream is composed of dust particles that have been ejected from a parent comet at a variety of velocities. These particles follow the same orbit as the parent comet, but due to their differing velocities they slowly gain on or fall behind the disintegrating comet until a shroud of dust surrounds the entire cometary orbit.




(B) Their orbits are uncontrolled by planetary gravitational fields.
(C) They become part of the meteor stream at different times.
(D) Their velocity slows over time.
(E) Their ejection velocity is slower than that of the comet.



6. The passage suggests that which of the following is a prediction concerning meteor streams that can be derived from both the conventional theories mentioned in line 18 and the new computer-derived theory?





(A) Dust particles in a meteor stream will usually be distributed evenly throughout any cross section of the stream.

both theories does not think particles “be distributed evenly throughout any cross section of the stream”


(B) The orbits of most meteor streams should cross the orbit of the Earth at some point and give rise to a meteor shower.

????
Whenever the Earth passes through a meteor stream, a meteor shower occurs.

(C) Over time the distribution of dust in a meteor stream will usually become denser at the outside edges of the stream than at the center.

Only new computer-model rather than conventional theories


(D) Meteor showers caused by older meteor streams should be, on average, longer in duration than those caused by very young meteor streams.
….correct


(E) The individual dust particles in older meteor streams should be, on average, smaller than those that compose younger meteor streams.
….out of scope







7. It can be inferred from the last paragraph of the passage that which of the following must be true of the Earth as it orbits the Sun?


On new computer-model’s side
Has the predicted twin-peaked activity been observed for the actual yearly Geminid meteor shower? The Geminid data between 1970 and 1979 shows just such a bifurcation, a secondary burst of meteor activity being clearly visible at an average of 19 hours (1,200,000 miles) after the first burst. The time intervals between the bursts suggest the actual Geminid stream is about 3,000 years old.




(A) Most meteor streams it encounters are more than 2,000 years old.
…..incorrect
Most meteor streams(this paragraph only talks about Geminid stream) it encounters are more than 2,000 years old.



(B) When passing through a meteor stream, it usually passes near to the stream’s center.
(C) It crosses the Geminid meteor stream once every year.
….correct

Thus we can infer the meteor stream’s age

(D) It usually takes over a day to cross the actual Geminid meteor stream.

….incorrect
…but it also can be 19 hrs or others

(E) It accounts for most of the gravitational perturbation affecting the Geminid meteor stream.




8. Which of the following is an assumption underlying the last sentence of the passage?


Has the predicted twin-peaked activity been observed for the actual yearly Geminid meteor shower? The Geminid data between 1970 and 1979 shows just such a bifurcation, a secondary burst of meteor activity being clearly visible at an average of 19 hours (1,200,000 miles) after the first burst. “The time intervals between the bursts suggest the actual Geminid stream is about 3,000 years old.”



(A) In each of the years between 1970 and 1979, the Earth took exactly 19 hours to cross the Geminid meteor stream.

…incorrect
The Geminid data between 1970 and 1979 shows just such a bifurcation, a secondary burst of meteor activity being clearly visible at an average of 19 hours (1,200,000 miles) after the first burst.

Every year between 1970-1979, “all exactly 19hrs”…..wrong
--we only know “average”, but we cannot say “all exactly 19hrs”, its too overgenerializtion




(B) The comet associated with the Geminid meteor stream has totally disintegrated.

….out of scope

(C) The Geminid meteor stream should continue to exist for at least 5,000 years.

….out of scope


(D) The Geminid meteor stream has not broadened as rapidly as the conventional theories would have predicted.

….incorrect
Here we’re not concerned with the rate of broadening

(E) The computer-model Geminid meteor stream provides an accurate representation of the development of the actual Geminid stream.
….correct



THIS IS A VERY TOUGH PASSAGE, if you're not major in astronological, you cannot quit grasp, in a very short time, the whole picture of what this passage really talks about, I try to use picture-visual rather than words to present this passage's idea by drawing a sketch attached below

Hi.
I got all the questions right except Q6. How is the ans (D) ?

Hey,

How much accuracy should one aim in RCs like this (someone mentioned this was 700+).

Regards,
Ajay

VeritasKarishma GMATNinja please help me with Q-6

The passage tells us:
Astronomers have hypothesized that a meteor stream should broaden with time ... The researcher found, as expected, that the computer-model stream broadened with time.

So both agree that the meteor stream broadens with time.
So when Earth passes through older meteor streams (which are broader), it will experience longer duration meteor showers (since Earth will take more time to cross a broader meteor stream)

Hence,

6. The passage suggests that which of the following is a prediction concerning meteor streams that can be derived from both the conventional theories mentioned in line 18 and the new computer-derived theory?

(A) Dust particles in a meteor stream will usually be distributed evenly throughout any cross section of the stream.
(B) The orbits of most meteor streams should cross the orbit of the Earth at some point and give rise to a meteor shower.
(C) Over time the distribution of dust in a meteor stream will usually become denser at the outside edges of the stream than at the center.
(D) Meteor showers caused by older meteor streams should be, on average, longer in duration than those caused by very young meteor streams.
(E) The individual dust particles in older meteor streams should be, on average, smaller than those that compose younger meteor streams.

(D) is correct.
_________________

can anyone explain question 5

Hi harshitajain,

Please refer the OE here: https://gmatclub.com/forum/a-meteor-str ... l#p2257837

Its 84th question in OE.

Let me know if you still have doubts.

Thanks.

Hi VeritasKarishma

I'm confused but the question was <<...derived from both the conventional theories mentioned in line 18...>>..
How come you cite <<Astronomers have hypothesized that a meteor stream should broaden with time ... The researcher found, as expected, that the computer-model stream broadened with time.>> since it's not conventional theories's assumption...?

Please help me
Thank you !

Astronomers have hypothesized that a meteor stream should broaden with time ...

This is the conventional theory. It is what astronomers have hypothesised.

The researcher found, as expected, that the computer-model stream broadened with time.

This is what they found on the computer model so it is the computer derived theory.

Both agree on this point.
_________________

Thanks for your reply VeritasKarishma !
I see the structure that you mentioned, “Astronomers have hypothesis that meteor stream should broaden with time” is Main idea here and Conventional theory is supporting idea so the conventional theory = Astronomer’s hypothesis.

However, what drives me crazy is that each “broaden with time” and “dense toward the center” demonstrates opposite direction.
I don’t understand how something can broaden with time, becoming denser towards the center. That’s why I thought astronomers’ assumption and conventional theory’s assertion are different.... Moreover, there is “however” after the conventional theory, putting more weight on the idea that they are going opposite direction.... ?

Posted from my mobile device